18 



Usinger: Introduction 



Thermal and trophic classifications are funda- 

 mental in nature and world-wide in application. At 

 the local level more detailed classifications become 

 feasible. For example, classifications may be based 

 on faunal affinities or methods of origin. Faunal 

 relations follow the same pattern for lakes as for 

 streams (intro. fig. 13), there being a Sierran and north 

 coastal Boreal region, a Great Basin region, a Central 

 Valley and south coastal California region, and a 

 southern Colorado desert region. 



The most conspicuous differences in California 

 lakes, however, are caused by differences in origin. 

 These are used as the basis for a classification of 

 the lakes of California. Illustrations (intro. fig. 20) are 

 from Davis (1933) who lists and discusses 129 of the 

 principal lakes and bays of the state. This, of course, 

 represents but a fraction of the lakes that are encoun- 

 tered, especially in the Sierra Nevada and the northern 

 Coast Range. 



Classification of the Lakes of California 



A. Lakes of Glacial Origin 



1. Ice-scoured highland lakes with shallow granite 

 basins. Desolation Valley Lakes. 



2. Cirque lakes. Hanging lakes carved out of 

 granite slopes and dammed with terminal mor- 

 aines. Upper Angora Lake. 



3. Trough-end lakes, with terminal and sometimes 

 lateral moraines. Donner Lake, Fallen Leaf 

 Lake, Convict Lake. 



B. Intermont Depression Lakes 



4. Fault-block and warped valley lakes dammed by 

 lava flows or landslides. Clear Lake, Lake 

 County. 



5. Intermont basin lakes with outlets. 



6. Playa lakes with no outlet and therefore saline, 

 sometimes below sea level. These are perennial 

 if the water supply exceeds that lost by evapora- 

 tion or intermittent, if the reverse. Mono Lake, 

 Honey Lake. 



C. Lakes of Volcanic Origin 



7. Crater lakes formed in the actual craters or the 

 collapsed cones of craters. Crater Lake (Oregon), 

 Crater Butte Lake, east of Lassen Peak. 



D. Limestone Basin Lakes 



8. Lakes formed by solution of limestone. 



E. River-made Lakes 



9. Oxbow lakes representing cut-off river meanders 

 in the delta regions of the Sacramento, San 

 Joaquin, and Colorado rivers. Murphy Lake 

 (Sacramento River), Lake Houghtelin (Colorado 

 River). 



10. Flood-plain Lakes. Basins adjacent to the flood 

 plain of the Sacramento River with extensive 

 reed marshes and with 20 to 100 square miles 

 of open water held in check by man-made dykes 

 after winter rains. Sutter Basin, Yolo By-Pass. 



11. Lakes barred by Fan Deltas. The saline Salton 

 Sea, a lake of fresh-water origin (in its present 

 form) separated by Colorado River delta-plain 

 from the marine waters of the Gulf of California. 



12. Coastal lagoons. Where rivers are blocked by 

 dunes and sand spits to form fresh or brackish 

 water lakes with or without direct connections 

 to the ocean at high tide. Merced Lake, Salinas 

 Lagoon, Abbott's Lagoon, Waddell Creek lagoon. 



Ponds 



There is no sharp distinction between lakes and 

 ponds. Sooner or later in the course of physiographic 

 evolution and eutrophi cation all lakes are destined 

 to become ponds unless climate and erosion reverse 

 the process. Generally speaking, ponds are small 

 bodies of water of little depth. Although they vary 

 in turbidity and therefore in penetrability of light, 

 ponds might be defined as entirely within the photo- 

 synthetic zone and at least potentially within the 

 zone of rooted aquatic plants. Or ponds might be 

 defined as entirely within the epilimnion, there being 

 no thermocline because all the water is within the 

 zone of wind circulation. 



In addition to ponds derived from lakes, there are 

 several types of naturally occurring ponds that arise 

 independent of lakes. Among these may be mentioned 



(1) pasture ponds of the Central Valley and elsewhere; 



(2) spring-fed ponds or basins throughout the state; 



(3) bare rock basins in high Sierran granite and else- 

 where; (4) snow-melt pools on rock or forest floor, 

 especially in the Sierra; (5) beaver ponds in Sierran 

 and some coastal streams; and (6) stream-fed pools 

 that become isolated in intermittent streams during 

 the summer and fall. 



Many ponds are perennial but pond organisms are 

 generally adapted to life under the rigorous conditions 

 of temporary ponds. Usually they have ready means 

 of dispersal, short life cycles, and resistance to 

 extremes of temperature, desiccation, and so on. 

 Several groups of insects are ideally suited to this 

 type of existence and as a consequence are the 

 dominant forms of life in ponds. Typical pond groups 

 are dragonfly nymphs, mayfly nymphs, true bugs, 

 beetles, and larvae of various groups of Diptera 

 including midges, mosquitoes, and the like. 



Lake and pond zones and communities. — Several 

 zones are recognized in standing waters. These are 

 of two main types: those associated with the shore 

 and bottom, and those associated with open water. 

 (Intro, fig. 21 shows the relationships of these zones.) 

 The littoral-benthic series ranges from the shore line 

 to the light compensation level — Littoral Zone, and 

 then to the Benthic Zone. In open water two zones 

 are recognized: the Limnetic Zone above the level 

 of light compensation (=photosynthetic or autotrophic 

 region) and the Profundal Zone (=decomposition or 

 heterotrophic region) below. These terms have been 

 borrowed from marine ecology and are not always 

 used in precisely the same sense by students of 

 fresh-water ecology. Insects occur in each of these 

 zones. For example, shore bugs (Saldidae) and Dixid 

 larvae live at the water's edge; caddis worms and a 

 host of other insects live in the littoral zone near 

 Shore; and bloodworms live in the benthic zone. In 



